Breast cancer is the second most common type of cancer (after lung cancer) and is the most common cause of cancer death among women worldwide. The number of breast cancer cases globally has increased significantly since the 1970s, a phenomenon partly blamed on modern lifestyles in the Western world, with the highest incidence occurring in North America. Women in the United States have a 1 in 8 (12.5%) lifetime chance of developing invasive breast cancer and a 1 in 35 (3%) chance of breast cancer causing their death. In 2007, breast cancer caused over 40,000 deaths in the U.S. The most life-threatening aspect of cancer is metastasis. Crucial steps in this disseminated process include cell migration and invasion of tumor cells into the vasculature and surrounding matrices. Metastatic cancers that spread to other tissues distant from the original tumor site are the most serious form of breast cancer. The most common place for breast cancer to metastasize is into the lymph nodes under the arm or above the collarbone on the same side as the cancer. Other common sites of breast cancer metastasis are the brain, the bones, and the liver.
Evidence suggests that at the time of diagnosis, a high proportion of patients already have micrometastasis. Early detection coupled with effective therapeutic intervention is crucial in surviving breast cancer. While breast cancer mortality rates have been gradually declining, due at least in part to improved screening and treatment methods, presently available diagnostic markers for breast cancer often fail to detect cancerous cells early enough for therapeutic intervention to prevent metastasis.
There is thus a need to identify mechanisms responsible for the metastatic process, diagnostic markers for breast cancer that enable early detection of cells exhibiting a metastatic phenotype, and therapeutic target(s) for inhibiting cancer cell migration and invasion.